A Study of the Induced Stress Caused by a Single Plug in a Yankee Dryer Shell Whilst Under Normal Operating Conditions, 2003 Fall Technical Conference

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Plugging is the method historically used for repair of surface defects in Yankee dryer shells. The practice for plugging requires an interference fit between the plug and the hole. While this practice has a long history of success, there have been a few cases where cracks have been observed in the shell adjacent to the plugged hole. The purpose of this study is to investigate the magnitude of the stress caused by this interference fit and the resulting stress around the plug hole after the application of operating loads. The stress results reported take into account the non-linear stress-strain behavior of gray cast iron. Both classical and finite element analyses agreed in predicting the magnitude of the stress at the edge of the plugged hole at very low strains. However, as the interference fit increased, the location of the maximum tangential stress moved away from the edge of the hole and the location the maximum stress did not change after the application of the operating loads. This result suggests that the applied paper making stresses saw not the original plugged hole, but rather a larger effective diameter described by the magnitude of the previously yielded volume of material.